databinding: Add an adapter for the KeyedObservableList

This adapter actually finally implements stable IDs correctly.

Signed-off-by: Samuel Holland <samuel@sholland.org>

app/src/main/java/com/wireguard/android/databinding/KeyedObservableListAdapter.java

@@ -0,0 +1,127 @@
+package com.wireguard.android.databinding;
+
+import android.content.Context;
+import android.databinding.DataBindingUtil;
+import android.databinding.ObservableList;
+import android.databinding.ViewDataBinding;
+import android.view.LayoutInflater;
+import android.view.View;
+import android.view.ViewGroup;
+import android.widget.BaseAdapter;
+
+import com.wireguard.android.BR;
+import com.wireguard.android.util.Keyed;
+import com.wireguard.android.util.KeyedObservableList;
+
+import java.lang.ref.WeakReference;
+
+/**
+ * A generic {@code ListAdapter} backed by a {@code KeyedObservableList}.
+ */
+
+class KeyedObservableListAdapter<K, E extends Keyed<? extends K>> extends BaseAdapter {
+    private final OnListChangedCallback<E> callback = new OnListChangedCallback<>(this);
+    private final int layoutId;
+    private final LayoutInflater layoutInflater;
+    private KeyedObservableList<K, E> list;
+
+    KeyedObservableListAdapter(final Context context, final int layoutId,
+                               final KeyedObservableList<K, E> list) {
+        this.layoutId = layoutId;
+        layoutInflater = LayoutInflater.from(context);
+        setList(list);
+    }
+
+    @Override
+    public int getCount() {
+        return list != null ? list.size() : 0;
+    }
+
+    @Override
+    public E getItem(final int position) {
+        if (list == null || position < 0 || position >= list.size())
+            return null;
+        return list.get(position);
+    }
+
+    @Override
+    public long getItemId(final int position) {
+        final K key = getKey(position);
+        return key != null ? key.hashCode() : -1;
+    }
+
+    private K getKey(final int position) {
+        final E item = getItem(position);
+        return item != null ? item.getKey() : null;
+    }
+
+    @Override
+    public View getView(final int position, final View convertView, final ViewGroup parent) {
+        ViewDataBinding binding = DataBindingUtil.getBinding(convertView);
+        if (binding == null)
+            binding = DataBindingUtil.inflate(layoutInflater, layoutId, parent, false);
+        binding.setVariable(BR.collection, list);
+        binding.setVariable(BR.key, getKey(position));
+        binding.setVariable(BR.item, getItem(position));
+        binding.executePendingBindings();
+        return binding.getRoot();
+    }
+
+    @Override
+    public boolean hasStableIds() {
+        return true;
+    }
+
+    void setList(final KeyedObservableList<K, E> newList) {
+        if (list != null)
+            list.removeOnListChangedCallback(callback);
+        list = newList;
+        if (list != null) {
+            list.addOnListChangedCallback(callback);
+        }
+        notifyDataSetChanged();
+    }
+
+    private static final class OnListChangedCallback<E extends Keyed<?>>
+            extends ObservableList.OnListChangedCallback<ObservableList<E>> {
+
+        private final WeakReference<KeyedObservableListAdapter<?, E>> weakAdapter;
+
+        private OnListChangedCallback(final KeyedObservableListAdapter<?, E> adapter) {
+            weakAdapter = new WeakReference<>(adapter);
+        }
+
+        @Override
+        public void onChanged(final ObservableList<E> sender) {
+            final KeyedObservableListAdapter adapter = weakAdapter.get();
+            if (adapter != null)
+                adapter.notifyDataSetChanged();
+            else
+                sender.removeOnListChangedCallback(this);
+        }
+
+        @Override
+        public void onItemRangeChanged(final ObservableList<E> sender, final int positionStart,
+                                       final int itemCount) {
+            onChanged(sender);
+        }
+
+        @Override
+        public void onItemRangeInserted(final ObservableList<E> sender, final int positionStart,
+                                        final int itemCount) {
+            onChanged(sender);
+        }
+
+        @Override
+        public void onItemRangeMoved(final ObservableList<E> sender, final int fromPosition,
+                                     final int toPosition, final int itemCount) {
+            onChanged(sender);
+        }
+
+        @Override
+        public void onItemRangeRemoved(final ObservableList<E> sender, final int positionStart,
+                                       final int itemCount) {
+            onChanged(sender);
+        }
+    }
+}